Guys, may I join the discussion? I've got a serious noise and will check the wiring, thanks for all the information shared.
Regarding the HU (Clarion CMD5). A yellow one, called memory lead, should be connected directly to the battery. That means - if I understand right - that this cable should be connected to the power source of the amps which is then finally connected to the dual battery switch.
At the moment I don't know where it is connected to at the moment. But is it ok to connect it to the + of the amp? Would the power on function still work? Guess yes since the amps are switched on via the blue/white cable (but get the power over red +, where finally the HU yellow is connected too).
There is another red cable at the HU which is called "switched power lead" and which should be connected to accessory 12+. Is it ok to connect to that cable for example another device such as a digital radio.
Thank you for your help